While personal privacy is an important concern for the public, it is sometimes very useful to let others identify you in the case of emergency. For example, if you were involved an accident and become injured, your medical treatment history is important information for health care providers to be able to immediately access.
Mobile phones and other mobile devices such as PDAs, are widely used by the population. There is a desire to exploit the widespread usage of mobile devices in order to easily identify people when the circumstances deem it necessary. On the other hand, there is a need to address the privacy issues surrounding the ability to identify people who do not wish to be identified or control the access on who may identify them and the purpose for the identification.